Linear power control systems generally have power control devices (e.g., transistors) that simultaneously have voltage across them and current through them. This condition causes poor efficiency and great dissipation in the devices. Switching power control systems avoid simultaneous voltage and current by reducing the time during which this condition occurs, by switching when voltage or current is at a reduced level, or some combination of these methods. Those situations in which switching is timed to occur with reduced voltage or current generally do so by selecting an operating frequency such that the reactive components designed in the circuit will cause the reduction at a known time, when switching takes place. The resulting high efficiency can be degraded by variations in frequency or component values, due to temperature, aging, unit to unit variations or other causes.